Fatal Clostridium septicum gas gangrene complicating ECMO: case report and review of literature

Abstract Clostridium septicum gas gangrene is a severe and deadly infection caused by an anaerobic, spore-forming, Gram-positive bacillus. As previously described, two entities are observed: traumatic and spontaneous (or non-traumatic) forms. In this report, we aim to describe the case of a fulminant and ultimately fatal C. septicum myonecrosis occurring in a patient who was first admitted for refractory cardiac arrest and placed on veino-arterial extracorporeal membrane oxygenation (ECMO). Building upon prior studies that have documented cases of spontaneous gas gangrene caused by C. septicum, we provide an updated compilation, focusing on microbiological characteristics of C. septicum, along with the diagnostic and therapeutic challenges associated with spontaneous gas gangrene. Additionally, the specific clinical situation of our case illustrates the seriousness of this infectious complication that combined both spontaneous and traumatic gas gangrene risk factors. We thus, discuss the antibiotic coverage prior to the initiation of ECMO procedure.


INTRODUCTION
Extracorporeal membrane oxygenation (ECMO) is a final resort method employed in the treatment of patients experiencing severe acute respiratory distress syndrome, cardiogenic shock or refractory cardiac arrest.The substitution system enables blood oxygenation using an external oxygenation membrane.Blood is withdrawn from the human body via a venous catheter and then reintroduced, following oxygenation, through a second venous or arterial catheter, creating a venous-venous or venous-arterial circuit [1,2].Despite significant progress in care and support of patient undergoing ECMO, mortality in intensive care units (ICUs) remains high: from 43 % in acute respiratory distress syndrome [3] to 61 % in cardiogenic shock [4].In refractory cardiac arrest cases, the long-term survival and neurological prognosis associated with ECMO effectiveness remains uncertain [5].
In this case report, we describe the fatal case of a male patient who was first hospitalized for refractory cardiac arrest requiring venous-arterial ECMO, which subsequently led to a C. septicum gas gangrene.To our knowledge, this is the first case in the literature.

OBSERVATION
We present the case of a 45-year-old male patient with no prior medical history, except for being overweight (BMI 28.9 kg m −2 ), who was hospitalized following a refractory cardiac arrest.The symptoms began 48 h before admission with the onset of epigastric pain and bronchial symptoms.He subsequently developed intermittent chest pain, described as burning, without radiation, along with pallor and sweating, prompting the initial call to emergency services.Cardiopulmonary arrest was confirmed by his partner at 04 : 45.Cardiopulmonary resuscitation was initiated immediately (no-flow <1 min).Medical team arrived at 5 : 08 and confirmed cardiopulmonary arrest due to ventricular fibrillation.Three external electrical shocks of 200 joules were delivered with no return to effective circulatory activity before intravenous administration of 300 mg of amiodarone and the first dose of epinephrine (1 mg) at 5 : 14.Orotracheal intubation was performed at 5 : 13, and the EtCO 2 was 48 mmHg.The patient was transferred to the University Hospital of Rennes while receiving automated external chest compressions.During the transfer, six additional external electrical shocks of 200 joules were administered, along with a second dose of intravenous amiodarone (150 mg) and intravenous lidocaine (90 mg).Signs of life were observed with limb flexion in response to stimulation and eye opening upon request.Upon arrival at our clinical centre at 6 : 21, there was no spontaneous circulatory activity.Veino-arterial ECMO was initiated at 6 : 38, resulting in a 90 min low-flow period.The femoro-femoral veino-arterial ECMO was established through direct surgical access of the right scarpa.A reperfusion cannula was inserted into the right superficial femoral artery.ECMO flow was set at 5 l min −1 with a r.p.m. of 3900 min −1 .The FmO 2 was set to obtain a SpO 2 ≥92 %.The correct position of cannula was confirmed by echocardiography and chest X-ray.No complications were reported.After haemodynamic stabilization, a coronary angiography revealed acute occlusion of the proximal and mid-right coronary artery.Thromboaspiration was followed by the placement of two active stents.Dual antiplatelet therapy with intravenous lysine acetylsalicylate (250 mg) and oral clopidogrel (600 mg) was initiated along with curative sodium heparin anticoagulation.Echocardiography showed diffuse akinesia, and sub-aortic valve systolic index was measured at 3.5 cm (with ECMO flow set at 5.0 l min −1 ).The initial evolution was marked by vasoplegia and hypovolemia due to post-resuscitation syndrome.The patient received 10 000 ml of crystalloid solution and norepinephrine up to 0.2 µg/ kg min −1 in the first day of intensive care.Sedation and neuromuscular blockade initiated at ECMO implantation were discontinued after 24 h of targeted temperature management (temperature maintained between 35 and 37 °C).Significant signs of awakening were observed with eye opening and limb movements upon request.Thirty-six hours after admission to ICU, the patient presented haemodynamic deterioration.Echocardiographic showed a significant improvement in overall left ventricular systolic function, and the sub-aortic valve systolic index was measured at 9 cm (ECMO flow set at 5.5 l min −1 ).Norepinephrine was gradually increased up to 1.25 µg/kg min −1 .Concurrently, severe hypoxemia (PaO 2 67 mmHg despite FiO 2 100 % and FmO 2 100 %) was observed.Chest X-ray revealed bilateral alveolo-interstitial opacities.Clinically, a unique purplish-violet lesion, 2 cm in size, was noted on the inner surface of the right leg.Empirical antibiotic therapy with a loading dose of 2 g of cefotaxime followed by a 6 g day −1 infusion and a 30 mg kg −1 dose of amikacin was initiated after blood cultures and endotracheal aspiration were performed.At 48 h after admission, epinephrine was added at a dose of 0.5 µg/ kg min −1 , along with an increase in norepinephrine to 2 µg/kg min −1 .Within an hour, a large, extended, and haemorrhagic bullous detachment was observed from the right leg to the right flank and perineum (Fig. 1).Subsequently, subcutaneous crepitus was noted on the right calf.
Hematologic tests then revealed anaemia with a haemoglobin level of 5.4 g dl −1 compared to 8.1 g dl −1 2 h earlier.Massive transfusion with seven units of red blood cells, seven units of fresh frozen plasma, and one unit of platelets was initiated in case of haemorrhagic complications.The clinical course deteriorated further with refractory shock, and surgical intervention was deemed futile.A pre-mortem computed tomography (CT) scan revealed emphysematous infiltration of the subcutaneous soft tissues, primarily intramuscular, of the right postero-lateral abdominal wall, extending to the right iliopsoas muscle and the right leg, and the right pectoral muscle.There was extensive emphysematous infiltration of the subcutaneous fatty tissues of the right leg, scrotum, and penis (Fig. 2).Air bubbles were present in the venous network of the right lower limb, extending to the right femoral vein, the inferior vena cava, and the left renal vein.Microbiological culture of endotracheal aspiration revealed a polymorphic flora.
Blood cultures and liquid from haemorrhagic bullae were incubated in both aerobic and anaerobic blood culture bottles.The anaerobic cultures revealed the presence of a Gram-positive, spore-forming bacillus.These anaerobic bottles were then subcultured onto agar plates under anaerobic conditions.Colonies were identified by MALDI-TOF mass spectrometry (Bruker Daltonics, Germany), with both samples yielding positive for C. septicum (Fig. 3).Antibiotic susceptibility was determined using the reference disc-diffusion method, according to 2022 CA-SFM/EUCAST guidelines, with Brucella  agar supplemented with 5 % sheep blood, 5 mg l −1 hemin, and 1 mg l −1 vitamin K. C. septicum was susceptible to all tested antibiotics: amoxicillin/clavulanate, piperacillin/tazobactam, imipenem, moxifloxacin, clindamycin, linezolid, vancomycin, and metronidazole (according to 2022 CA-SFM/EUCAST clinical breakpoints).The patient succumbed 58 h after hospital admission.

Clostridium septicum
C. septicum is an opportunistic, anaerobic, spore-forming Gram-positive bacillus.These spores represent the resistance and dissemination form of Clostridium species.It is often found in the soil and in animal digestive tracts [17,23,25].Whether C. septicum is a normal commensal bacteria in the human gut remains unclear, however carriage frequency appears to be low [26].

Virulence and toxins
C. septicum exerts several important bacterial factors involved in its virulence.In contrast to other Clostridium species, such as C. perfringens, C. septicum displays an aerotolerant metabolism, thus explaining its ability to proliferate in healthy tissues, even in the absence of a strict anaerobic environment [27].In a murine model, the bacterial load necessary to cause infection is 300fold lower than with C. perfringens, and with only a few quantities of spores it can cause fatal disease in immunocompromised patients [27,28].Like many flagellated bacteria, C. septicum has the ability to develop collective mass swarming behaviour, notably in nutrient-restricted conditions [29], participating to coordinate movements on surfaces, thereby facilitating tissue invasion [29].Additionally, C. septicum demonstrates the capacity to form biofilms through several features like flagella or biofilm-associated proteins, showing positive correlation with antibiotic resistance and resulting in a worse prognosis [28].C. septicum virulence relies mostly on the synthesis of a necrotic exotoxin called α-toxin which is coded by the csa gene [30][31][32].It belongs to the aerolysin family, like the ε-toxin produced by C. perfringens and a toxin secreted by Aeromonas hydrophila [17,20,25].It is initially secreted as an inactive preprotoxin state, subsequently activated by various host proteases, resulting in oligomerization and formation of membrane pores leading to programmed cellular necrosis [17,20,31,33].These membrane pores play a crucial role in tissue necrosis, leading to osmotic cell lysis and an intracellular influx of Ca 2+ ions, initiating a signalling cascade resulting in programmed cell necrosis [34].Additionally, α-toxin leads to decreased tissue perfusion, paving the way for anaerobic conditions to emerge.It also reduces the chemotactic response of neutrophilic polymorphonuclear leukocytes at the site of infection.This toxin induces an increase in capillary permeability, probably explaining frequent metastatic dissemination.Furthermore, α-toxin actively promotes the secretion of HMGB1, a protein that affects neutrophil-dependent antibacterial mechanisms and may participate in the development of a fulminant septic state [16,17,20,[34][35][36]. C. septicum also produces other enzymes including β-toxin (DNAse), γ-toxin (hyalurodinase) or δ-toxin (hemolysin), that may contribute to an increased capillary permeability, myonecrosis and toxin dissemination [28].C. septicum displays many other virulence factors as neuraminidase, protease, sialidase or fibrinolysin which may contribute to systemic dissemination through tissue damages [17,28,37,38].

Antibiotics susceptibility
Data on C. septicum remains limited in the literature.It is usually susceptible to penicillin or metronidazole [12,[39][40][41].In contrast to C. butyricum, C. clostridioforme, C. ramosum or C. innoccum, no β-lactamase has been described in C. septicum.However, resistance to other antibiotics has been described.In a study involving 78 strains, 24.3 % showed resistance to vancomycin [28].Moreover, resistance to clindamycin appears to be more prevalent, as resistant strains are observed in multiple studies (ranging from 34.6-69 % of tested isolates) [28,41,42].

Pathophysiology
Gas gangrene is a deadly disease, showing high mortality (67-100 %), especially in the first hours [12,17].Spontaneous gas gangrene occurs without any major external trauma.Most of these spontaneous necrotic infections are caused by C. septicum, and several host factors, especially immunosuppression conditions, favour its development [17].In 2017, Srivastava et al. [17] showed that in patients with spontaneous gas gangrene, 71 % had an underlying malignancy, mostly digestive [17].The principal hypothesis explaining the high correlation between spontaneous gas gangrene and cancer or immunosuppression lies on the probable association between a transient carriage and host factors.This may result in increased colonization and/or higher susceptibility to infection [17].Tissue destruction generated by C. septicum virulence factors maintains an anaerobic environment, allowing bacterial multiplication associated with gas production leading to clinical crepitus, characteristic of clostridial gas gangrene [35,43].

Clinical presentation
Clinical features are characterized by progressively increasing muscular pain, often disproportionate regarding clinical impact and mostly affecting limbs 18,27].Clinical deterioration appears to be faster than with C. perfringens [27] and rapidly leads to apparition of haemorrhagic bullae, as observed in our case, change in skin coloration and the emergence of tissular necrosis [17].It is important to note that gas crepitus is not systematically present at diagnosis, and may occur in late stages of the infection [17,[44][45][46].Timeline between infection and necrosis can be fulminant and can last between 6 to 48 h [18,35,44,47].Progression to septic shock, multi-organ dysfunction and death often occurs rapidly (< 24 h), and mortality rates are higher in myonecrosis secondary to C. septicum (79 %) than in those caused by C. perfringens (32 %) [35].

Diagnosis
Diagnosis of spontaneous gas gangrene can be difficult, mainly due to the lack of a clear entry point, the non-specific initial symptomatology and the rapid evolution toward septic shock.Mean time of incubation is between 12 to 24 h and myonecrosis can extend as fast as 2 cm per hour [17,48].The diagnosis relies on clinical criteria, as imaging and microbiological samples must not delay medical care [44].Disparity between severe pain and clinical presentation, rapid haemodynamic deterioration, onset of haemorrhagic bullae or skin necrosis should raise suspicion of necrotic involvement of soft tissues [43,49].The input of imaging must be restricted to situations where clinical presentation is unclear.However, it should not delay any surgical or medical care [43,47].X-ray radiography could contribute to faster identification of gas into tissue [35], but this technique shows low sensitivity [44,50], as does ultrasound imaging [43,47].CT scan has the ability to characterize tissue impairment, reveal gas or evaluate infection evolution.Finally, MRI is an effective method to identify soft tissue necrosis, but access times are often incompatible with emergency situations and CT scan is generally preferred [45,47,51].Surgery is also crucial in diagnosis, allowing confirmation of tissular necrosis and microbiological sampling.The identification of spore-forming Gram-positive bacilli should prompt to antibiotics stewardship [17,18,45].*Diabetes can be associated with immunosuppressive underlying condition.

Therapeutics
The management of these gas gangrenes relies on a medical-surgical approach, where the debridement of necrotic tissues remains the absolute emergency [17,18,46].Survival is increased in patients for whom surgery occurs within the first 24 h post-admission, even more within 6 h [46,50].Medical approach includes probabilistic antibiotic therapy as Infectious Diseases Society of America (IDSA) recommends the use of a large-spectrum association of molecules: vancomycin +piperacillin/tazobactam or a carbapenem.A combination of intravenous penicillin (2-4 million unit/4-6 h) and clindamycin (600-900 mg/8 h), due to its anti-toxin activity, is therefore recommended when Clostridium spp. is identified [18,46,50,52,53].
The place of hyperbaric oxygen in management of gas gangrene remains discussed since the lack of animal and clinical data does not allow for its clear role in those infections.Furthermore, as C. septicum exhibits better aerotolerance, hyperbaric oxygenation is actually not recommended and should not delay surgical intervention [17,18,43,46,50,52].Finally, as underlying diseases are often associated with spontaneous gas gangrene, investigation must be done when patient's condition allows for it.

Review of C. septicum spontaneous gas gangrene literature
In 2017, the review of Srivastava et al. [17] focused on 94 C. septicum spontaneous gas gangrene cases, from 1956 to 2016.

DISCUSSION
To our knowledge, this is the first case of C. septicum gas gangrene following veino-arterial ECMO cannulation.In our report, the source of infection appears to be related to the ECMO implantation site.However, an endogenous origin cannot *Patient with septic shock were included in both hypotension and tachycardia criteria.
be ruled out, as low-flow can favour anaerobic conditions, digestive ischemia and bacterial translocation.The rapid and fatal progression of this case raises the question about antibiotic prophylaxis of such life-saving surgical interventions.Indeed, the timing of ECMO implantation is an integral part of low-flow and justifies a need for speed.Despite implantation in a dedicated medical environment, disinfection and demarcation of the operative site with sterile drapes, early infections can still result from inadequate asepsis.Furthermore, the high risk of bacterial infection in the early phase of ECMO implantation, associated with the potential of bacterial translocation due to prolonged no-flow (particularly splanchnic) in the specific case of refractory cardiac arrest could justify antibiotic prophylaxis.Current recommendations (ELSO, Extracorporeal Life Support Organization) do not advocate for antibiotic prophylaxis for these procedures [84].However, if antibiotic coverage is initiated, it is not recommended to extend it beyond 48 h [84].Despite the lack of recommendations, 50-68 % of teams still use antibiotic prophylaxis.The most common antibiotics used are cephalosporins, penicillin, vancomycin or aminoglycosides [1].Notably, there is no clinical data available on the efficacy of these protocols and administration prior to ECMO implantation does not appear to be associated with a decreased infection risk [1].

CONCLUSION
Gas gangrene due to C. septicum is extremely serious disease, often fatal, and has never been described in the context of extracorporeal circulation.Such an invasive procedure is considered as 'clean' procedure (Altemeier class 1) for which no antibiotic is currently recommended.However, in the context of cardiac arrest, as presented in our case, several factors may explain the development of this C. septicum gas gangrene.The fatal outcome of this case could raise the question of using anti-clostridial antibiotics in the coverage of ECMO intervention, but the scarcity of described cases and current data do not allow the drawing of any conclusions and would require further studies.

Fig. 1 .
Fig. 1.Images of the right leg, right flank and perineum.

Table 1 .
Summary of features of C. septicum spontaneous gas gangrene cases between 2017 and 2022

Table 2 .
Underlying disease, treatment and blood cultures results of C. septicum spontaneous gas gangrene cases between 2017 and 2022

Table 3 .
Summary of clinical features during hospitalization